Field of the Disclosure
Embodiments disclosed herein generally relate to plasma processing systems and materials and apparatus for controlling plasma uniformity in plasma processing systems.
Description of the Related Art
Plasma processing chambers are regularly utilized in various electronic device fabrication processes, such as etching processes, chemical vapor deposition (CVD) processes, and other processes related to the manufacture of electronic devices on substrates. Many ways have been employed to generate and/or control the plasma density, shape, and electrical characteristics in processing chambers, such as capacitively or inductively coupled RF sources commonly used in conventional plasma chambers. For example, during a plasma-enhanced chemical vapor deposition (PECVD) process, process gases are introduced into a processing chamber through a capacitively coupled showerhead that is disposed over a semiconductor substrate that is circumscribed by a process kit. Once a plasma is formed in a PECVD chamber, the plasma and process gas(es) interact with the substrate to deposit a desired material layer thereon.
Conventional plasma processing chamber designs in which the generated plasma is disposed over the substrate surface can cause unwanted sputtering and damage to the substrate surface due to the interaction of electrons and ions formed in the plasma with the substrate surface. Floating and electrically grounded components that are exposed to the generated plasma will generally accumulate a net charge. The formed net charge causes electrons and/or ions formed in the plasma to bombard and possibly damage the exposed surfaces of the substrate or chamber component. Thus, in some applications it is desirable to form gas radicals that have sufficient energy to easily react with the substrate surface, or surface of the chamber component, to enhance the reaction rate, while not energetically bombarding the surface of the substrate or chamber component, since the non-ionized gas radical is not affected by charge formed on the substrate or component surface.
Therefore, to prevent or minimize the plasma interaction with the substrate and chamber components, remote plasma source (RPS) designs have been developed. Typical remote plasma source designs include a plasma generation region that is remotely positioned from the processing region of the processing chamber in which a substrate is positioned. In this way the plasma generated in the plasma generation region of the RPS device will generally not interact with the substrate surface.
However, conventional RPS designs typically utilize microwave, capacitively coupled, or inductively coupled energy sources that have a narrow plasma generating region, which will cause these devices to have a smaller than desirable plasma processing window that limits the range of energies of the formed gas radicals and gas ion that are formed in the plasma generating region of the conventional RPS device. Conventional RPS designs traditionally use a closed loop RF source configuration having windings that are wrapped around a closed magnetically permeable core that surrounds a portion of the plasma generating region. In one example shown in FIG. 1, which corresponds to FIG. 3 of the issued U.S. Pat. No. 6,150,628, a conventional RPS design will generally include regions 112, 114 of a metallic plasma chamber 100 in which a plasma is generated by the delivery of energy to a first and a second core 104, 106. The generated fields, which are focused by the position and shape of the cores 104, 106 relative to the regions of high activity “PR,” have a relatively small area and have a very limited time in which to transfer the RF energy to a gas flowing through the conventional RPS device. Thus, conventional RPS designs with a small plasma generating region have a very limited ability to generate and/or control the energies of the formed gas radicals and/or gas ions.
To resolve the energy coupling efficiency problems, typically, conventional RPS devices may require both electro-negative type gases (e.g., ammonia (NH3)) and electro-positive type gases (e.g., argon (Ar)) to flow at the same time through the plasma generation region to more easily form and sustain a generated plasma therein. However, this requirement may limit the ability of the RPS device to perform different process applications, as in some cases it is desirable to only deliver a single electro-negative or a single electro-positive gas to improve the processing speed or plasma processing results. Also, it is often desirable to form and sustain a plasma within regimes that have a low plasma impedance, such as where the pressure in the plasma generation region is low (e.g., <200 mTorr). Conventional RPS designs that inefficiently couple the plasma energy to the processing gasses are not currently able to meet the needs of the semiconductor processing industry. Therefore, there is a need for an RPS design that more effectively couples the delivered RF energy to the processing gases, has a wider process window and is able to work in a wider range of plasma impedances.
Conventional RPS designs are generally not able to tune power delivered to the plasma without also altering other process conditions. For example, a conventional RPS design may increase power delivery by mechanically inhibiting gas flow of the plasma generating region, so that the gas atoms have a longer dwell time in the generated electric fields. However, this slowed flow will also increase pressure in the plasma generating region, which may cause deleterious or at least sub-optimal effects on the plasma and/or the processing. This interrelation seen in conventional RPS designs makes it particularly difficult for a conventional plasma source to support multiple process applications and cleans.
Additionally, there is a need in the art for an apparatus and process that more effectively generates and controls plasma uniformity and has a larger processing window, without significantly increasing processing or hardware costs.